The present invention relates generally to an apparatus and method for applying a finishing block to a lens, such as an eyeglass lens, in registration with reference data on the lens. More particularly, the invention relates to such an apparatus and method wherein an alignment pattern is provided which includes a visual representation of acceptable tolerances in the position of the optical center of the lens and the amount of prism in the lens.
Commonly assigned patent application Ser. No. 08/718,153, filed on Sep. 24, 1996 and herein incorporated by reference, discloses an apparatus for attaching a finishing block to a lens in registration with reference data present on one surface of the lens. The reference data may take the form of markings applied to the lens indicating, for example, the optical center and the 0-180.degree. axis of the lens. The reference data may also include physical structure such as a bifocal segment defined by the surface of the lens.
The apparatus includes a display for projecting an alignment pattern representing characteristics of the lens along an image path. An operator places the lens in the apparatus with the reference data on the lens aligned with the corresponding characteristics of the lens represented in the pattern. When the operator has positioned the lens in the apparatus with the reference data properly aligned with the pattern, the apparatus will automatically attach the finishing block at the correct location on the lens. Once the finishing block is attached, the lens is placed in an edging device for further processing.
Alignment of the reference data on the lens with the pattern does not provide any indication as to whether the optical center of the lens is properly located or whether the lens has the required prism. In the case of an eyeglass lens, for example, the ophthalmologist or optometrist cannot determine if the lens conforms to the specified prescription until the lens is finished, inserted into an eyeglass frame and fitted to the patent.